seems to have happened to so many after the last update. I didnt need or want the update but when my pc started to freeze every time i went to Itunes i thought i would give it a go - then lost all my tracks. The phone help via Apple said this was not possible and since I didnt have a Mac they could not help me get back what was lost. I searched via Itunes for what I could, but then, once i sorted a couple of lists out, i went to play a track off my desk top and it froze again.
Itunes did say that they should be able find anything bought via their store but most of my stuff was music I created and well organised samples or collaborations.
I went to all my downloads section of the computer, found what I had downloaded via different sites, found another way to play music instead of Itunes and now I do not have any more problems with freezing or losing tracks etc
problem solved